Box hole boring machines are used in the underground drift of a mine for robbing ore material which is located in a substantially vertical direction above the machine. A cutterhead is attached to the upper end of an extensible drive shaft or drill stem, and a hole is cut which may be precisely vertical or which may be inclined at an angle of 10, 20 or more degrees from the vertical.
An effective machine of this type may utilize a cutterhead which weighs several tons. The cutterhead is generally transported to the mine, and attached to the machine, as a single unitary structure. Since the cutterhead operates at elevations above the machine itself, the attachment of the cutterhead to the machine in the first instance requires lifting the cutterhead upward from the floor of the drift, moving it horizontally over the machine, and aligning it correctly with the machine so that attachment is possible.
Available working space within means is inherently very limited. A conventional crane cannot be used for attaching the cutterhead to the boring machine, because the crane would be much too large to be received in the mine drift. Likewise, a conventional fork lift machine is too large to fit into the available space.
The conventional practice, therefore, has been to make a custom installation of fastening devices into the rock walls or ceiling of the tunnel, and then attach a lifting sling to these fastening devices. This previously utilized procedure for installing the cutterhead has been slow, cumbersome, and unduly expensive.
The object and purpose of the present invention, therefore, is to provide an economical and efficient method and apparatus for handling and aligning a heavy cutterhead, and attaching it to its associated box hole boring machine, within the limited working space of a mine drift or tunnel.